Improvements in medical imaging technologies, such as MRI, CT and ultrasound, have made it possible to image internal anatomical features in ways that show both structure and motion. Better diagnosis of certain medical conditions, such as heart disease, generally requires imagery that may be acquired quickly, and that provides information pertaining to both anatomical structure as well as function. Accordingly, there is an ongoing need for quantitative imaging of various tissue regions, such as the heart or other organs, which reduces the subjectivity and dependence on the experience of the reading physician.
Magnetic Resonance Imaging (MRI) has become a leading means of imaging for noninvasive diagnostics. By operating in regions of the electromagnetic spectrum that are benign to tissue, MRI imagery may be acquired repeatedly without danger to the patient. As used herein, the term “imagery” may refer to a single image or multiple images.
Non-MRI medical imaging technologies are generally not well suited for observer-independent imaging. These technologies, such as ultrasound, may involve invasive devices or cutaneous probes that may apply pressure to the patient's body in the vicinity of the tissue being imaged. As such, these imaging technologies may interfere with the function of certain organs by applying pressure, causing tissue deformations that may interfere with the motion and function of the tissue being imaged.
Existing MRI procedures are lengthy (at least 20 minutes) and involve the placement of patients inside the bore of the magnet for at least this duration of time. This has a number of disadvantages. The placement of a patient inside a closed bore magnet, which provides the best quality for imaging the heart, is extremely inconvenient for the patient and is very sensitive to any motion of the patient. Compliance to the restriction of remaining still for extensive periods of time is extremely difficult for patients to maintain; as a result, acquired images of the heart frequently suffer from lower image quality. Also, extensive time inside the magnet is completely troublesome for many patients with different degrees of claustrophobia, which can cause additional motion that interferes with the imaging quality and can cause premature interruption or termination of the imaging, rendering the diagnostic information worthless.
Besides the length of the stay inside the magnet, the acquisition of different images should be carried out with no patient motion, including breathing, during the scan. This requires patients to hold their breath for periods of about 10 seconds and repeat them many times while staying still within the magnet bore.
This complexity of imaging with a need of high compliance of patients reduces significantly the quality of the resulting images of the heart, which results in significant variability between the readers who assess the diagnostic information contained within the images subjectively.